A wireless sensor actuator network comprises a plurality of field devices embedded with sensor nodes, distributed spatially in a process plant. During joining of the field devices into the wireless sensor actuator network, security considerations regarding integrity, confidentiality and authentication of the connection have to be addressed. Another aspect that needs to be considered is the time for joining/rejoining of the field devices to the wireless sensor actuator network which is a critical parameter indicative of the performance of the wireless sensor actuator network. As per state of art, the time for joining or rejoining of a field device becomes longer when security is more complex. For instance, in a standardized communication protocol like the Wireless Highway Addressable Remote Transmitter communication protocol, more commonly referred to as the WHART, the field device joining process is secured by a 128 bit AES encryption mechanism, which results in longer time for joining or rejoining of the field device.
In general, configuring and joining of a field device to the wireless sensor actuator network is often involves a series of time consuming processes which provide a high level of reliability in the delivery of data while sacrificing temporal efficiency. Generally, the time for joining of a field device to a wireless sensor actuator network is divided into the configuration time and the joining time. The time taken for configuring of the field device initially, using maintenance port is the configuration time, and the time taken for the field device to become part of the wireless sensor actuator network is the joining time. Conventionally, the joining process for the field device includes a plurality of steps such as communicating with the network manager, advertising of joining request, receiving an acknowledgement and allocating the session key after joining the network. The exchanging of network credentials like network ID, join key, session key, network key, Graph ID and slot number by the field devices and the network manager is done automatically over the air during the joining process. In light of the mentioned steps, the time for joining is affected by a plurality of indeterminate parameters like non-availability of the network manager, network size, number of hops in the wireless sensor actuator network, distance from the gateway, device processing speed, etc., therefore resulting in inefficient and unpredictable joining.
Therefore, in light of the above discussion, there is a need for a method and system for joining of a field device into a wireless sensor actuator network.